Tumour necrosis factor alpha is pro-inflammatory in normal human skin and modulates cutaneous adhesion molecule expression

Tumour necrosis factor a (TNF-α) is a potent immunoregulatory cytokine produced by many cutaneous cells, including kcratinocytes, mast cells and Langerhans cells. To explore its potential role in inflammatory skin disease, we have studied immunohistochemically the effects of intradermal recombinant human TNF-α (rHuTNF-α) on cutaneous inflammatory cells, adhesion molecules and Langerhans cells in normal human skin. Volunteers received rHuTNF-α 100U (group A), 5000 U (group B), or 100 U daily for 5 days (group C), and biopsies were taken at 6 h (groups A and B), or 6 h after the final injection (group C). An inflammatory cell infiltrate developed in all cases: following single injections of either 100 or 5000 U rHuTNF-α this was predominantly neutrophilic, whereas following multiple injections of 100 U few neutrophils were seen, although many lymphocytes (CD3⁺, CD4⁴) were present. In all groups there was an increase in cells of monocyte/macrophage lineage (CD36⁾⁺. TNF-α induced a dose- and time-dependent decrease in CDla⁺ epidermal Langerhans cell numbers and an increase in dermal CDla⁴ cells, suggesting migration of Langerhans cells away from the epidermis. TNF-α induced endothelial E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in all groups, and adhesion molecule expression by interstitial dermal dendritic cells (ICAM-1 and VCAM-1) and keratinocytes (ICAM-1) was observed. These findings indicate that TNF-α is a potent modulator of cutaneous immune function in vivo, and this central role in the cutaneous immune response suggests that TNF-α may be an attractive target for therapeutic inhibition.     

The ICAM-3/LFA-1 interaction is critical for epidermal Langerhans cell alloantigen presentation to CD4+ T cells

Intercellular adhesion molecule (ICAM)-3 is a recently described member of the immunoglobulin superfamily and, as such, is closely related to ICAM-1 and ICAM-2. All three ICAMS are cognate for the counter-receptor lymphocyte function associated antigen-1 (LFA-L CD11a/CD18). Unlike ICAM-1 and ICAM-2. ICAM-3 is constitutively expressed at high levels on resting leucocytes. We investigated the expression and function of ICAM-3 in normal skin (n= 5), as well as its expression in psoriasis (n= 4). atopic eczema (n= 4), allergic (rhus) contact dermatitis (n=3). and cutaneous T-cell lymphoma (CTCL. n=2). Five-micrometre cryostat sections of skin were stained using monoclonal antibodies to ICAM-3 and A well characterized immunoperoxidase technique. In normal skin. ICAM-3 was expressed by all cutaneous leucocytes hut most striking was the strong expression of ICAM-3 by Langerhans cells within both epidermis and dermis. This observation was confirmed by double-labelling with CD1a and negative staining with an IgG1 isotype control. In psoriasis, atopic eczema, allergic contact dermatitis, and CTCL. ICAM-3 was co-expressed on all CD1a⁺ cells, although, in psoriasis, the intensity of ICAM-3 expression was reduced. Functional blocking experiments were performed to determine whether the observed ICAM-3 expression on Langerhans cells was functionally important in antigen presentation. CD4⁺ T cells were prepared from peripheral blood and 10⁵ CD4⁺ T cells combined with 10⁵ epidermal cells harvested from keratome biopsies of normal skin of an individual allogeneic to the T-cell donor. Addition of 50 μg anti-ICAM-3 to the co-culture resulted in a consistent (50%) reduction in degree of alloantigen presentation by Langerhans cells to T cells. Inhibition was 77% of that produced by the addition of anti-LFA-1. These data indicate that ICAM-3 is constitutively expressed by Langerhans cells and is a major ligand for LFA-1 on CD4⁺ T cells during their response to Langerhans cells. Because fresh Langerhans ceils constitutively express little ICAM-1. whereas ICAM-3 is constitutively expressed at high levels, it would appear that 1CAM-3 is the dominant functional ICAM on in situ Langerhans cells in the normal epidermis.     

IL-10 inhibits ICAM-1 expression on human Langerhans cells but not on keratinocytes, dermal endothelial cells or fibroblasts

Abstract Intercellular adhesion molecule-1 (ICAM-1) is regularly expressed or inducible on all major cutaneous cell populations including Langerhans cells, keratinocytes, endothelial cells and dermal fibroblasts. ICAM-1 is induced in the skin under inflammatory conditions and plays an important role in the activation of T cells. Interleukin-10 (IL-10) is a pluripotent immunosuppressive cytokine that inhibits proliferation of T cells via inhibition of antigen-presenting cells including Langerhans cells. We demonstrates that IL-10 inhibits baseline and also cytokine-stimulated ICAM-1 expression on human Langerhans cells, which has previously been shown in the murine system. No effect of IL-10 was seen on human dermal vascular endothelial cells, which like Langerhans cells are also able to present antigen. Additionally, no inhibitory effect of IL-10 was observed on the ICAM-1 expression of keratinocytes and dermal fibroblasts. As IL-10 only weakly suppresses MCH II on human Langerhans cells, inhibition of ICAM-1 and other accessory molecules by IL-10 seems to be an important mechanism inhibiting the antigen-presenting function of human Langerhans cells. Received: 9 December 1997     

Increased expression of adhesion receptors in both lesional and non-lesional psoriatic skin

Adhesion receptors and their ligands play a vital role in the immune system. We studied the expression of different adhesion receptors, using single- and double-staining immunohistochemical techniques, in both lesional and non-lesional skin specimens from seven psoriasis patients and in skin biopsy specimens from eight normal healthy controls. Our results showed an overall increased expression of several adhesion receptors in both lesional and non-lesional psoriatic skin. We consistently found an increased expression in particular of ICAM-1 and E-selectin on endothelial cells, and ICAM-1 on T cells and Langerhans cells. In contrast, a weak expression of VCAM-1 was found on endothelial cells and mononuclear cells in lesional psoriatic skin specimens alone. Interestingly, LFA-1 was also expressed on Langerhans cells, with a greater frequency in skin from lesional than from non-lesional sites, but was never expressed in skin from normal healthy individuals. Furthermore, significantly increased numbers of Langerhans cells and T cells with a positive reactivity for MAb HECA-452 were found in both lesional and non-lesional psoriatic skin. We hypothesize that the enhanced expression of adhesion receptors on migrating immunocompetent cells and endothelial cells of psoriatic skin in general facilitates the increased influx of activated T lymphocytes and other immunocomponent cells into the skin, and thus underscores the generalized character of the disease.     

Immunohistochemical analysis of chronic discoid and subacute cutaneous lupus erythematosus—relation to immunopathological mechanisms

An immunohistochemical analysis of skin biopsies was performed in 18 patients with cutaneous lupus erythematosus (LE), using the alkaline phosphatase and monoclonal anti-alkaline phosphatase method (APAAP). The study group was subdivided on the basis of clinical criteria into 10 patients with chronic discoid LE (CDLE) and eight patients with subacute cutaneous LE (SCLE). Using a panel of monoclonal antibodies the following results were obtained: (i) ICAM-1 was expressed on epidermal keratinocytes, dermal inflammatory cells, and endothelial cells in most biopsies, whereas LFA-1 was confined to the dermis. Attachments between keratinocytes or endothelial cells and activated T lymphocytes via ICAM-1/LFA-1 may be a possible mechanism of target/effector recognition in cutaneous LE. (ii) HLA-DR was expressed on epidermal keratinocytes and cells of the dermal infiltrate, but not on endothelial cells. HLA-DR⁺ cells probably function as antigen-presenting cells, leading to major histocompatibility complex-restricted cellular cytotoxicity in cutaneous LE. (iii) Interleukin 2 receptor expression on dermal inflammatory cells was weak, indicating non-specific activation of T lymphocytes. (iv) The dermal inflammatory cells were T lymphocytes, mainly of the helper/inducer subtype. B lymphocytes were rarely found in the dermis. In general, no significant immunohistochemical differences were found between CDLE and SCLE, suggesting that these variants represent clinical subtypes rather than different pathogenetic entities.     

Expression of a cell adhesion protein (VLA β) in normal and diseased skin

Biopsies from normal skin (n = 17) and various cutaneous disorders (n = 83) were examined immunohistologically for reactivity with an antibody (CD29) against the common beta chain of the VLA integrin family. In normal skin, CD29 recognized a number of cell types, i.e. endothelial cells, fibroblasts, T lymphocytes and basal keratinocytes. Similar cells were positive in diseased skin, but the expression of VLA beta was upregulated on keratinocytes. The phenotype of the VLA beta-positive T cells was examined in more detail by staining with anti-T-cell antibodies, i.e. CD3, CD4, CD8, CD45RO (UCHL1) and CD45R (2H4). These studies showed that most of the T cells in normal skin, benign cutaneous conditions and early cutaneous T-cell lymphomas (CTCL) expressed a similar phenotype and resembled antigen committed 'memory' (helper/inducer) cells (CD4+, CD29+, CD45RO+, CD45R-). In advanced CTCL, expression of these antigens was more variable, and many of these infiltrates showed aberrant (or unusual) expression of CD29, CD45RO, CD45R and other T-cell antigens. It is concluded that several cells involved in cutaneous immune reactions express a molecule (VLA beta) which acts as a receptor for extracellular matrix components. This molecule is important for the attachment of cells to connective tissue constituents and may act to facilitate the migration of lymphocytes (and other cells) during immune reactions in normal and diseased cutaneous conditions. Advanced CTCL differ from the early lesions and it is possible that there is a progressive accumulation of increasingly malignant (or transformed) cells in these conditions.     

Immunohistology of skin pathergy reaction in Behçet's disease

Summary The immunophenotypic characteristics of the skin pathergy reaction (SPR) at 48 h in Behçet's disease (BD) were investigated in 12 patients with BD and in five controls. The findings in 11 positive and one negative SPR lesions of patients with BD were evaluated in comparison with those of normal adjacent skin and with the negative pathergy biopsies from the controls. Positive SPR biopsies showed variable epidermal thickening and cell vacuolization, as well as subcorneal pustule formation. In the SPR dermis, a variable dense focal mononuclear cell (MNC) infiltrate was seen around vessels and skin appendages, extending into the deep dermis. The MNC infiltrate was predominantly composed of T lymphocytes and monocytes/macrophages. The majority of the T lymphocytes were CD4⁺, and almost all expressed CD45RO. Approximately half of the infiltrating cells strongly expressed HLA-DR. Neutrophils constituted less than 5% of the infiltrating cells, but were present as clusters of elastase-positive cells at the needle-prick sites. Vessels within the lesion showed marked congestion and endothelial swelling. The endothelial cells expressed ICAM-1 strongly, and E-selectin moderately. VCAM-1 was not expressed on endothelial cells. The basal and mid-epidermal layers of keratinocytes expressed HLA-DR and ICAM-1 strongly, particularly so in areas close to the dermal MNC infiltrates. In negative pathergy biopsies, there were increased numbers of neutrophils and a few small clusters of macrophages and T lymphocytes only at the needle-prick site, and the endothelial cells of vessels close to these areas expressed E-selectin weakly. The immunohistological findings of the SPR appear to indicate an augmented antigen-independent non-specific induction phase of the inflammatory response. Absence of VCAM-1 expression by endothelial cells suggests that direct epidermal injury is the cause of the cutaneous inflammation.     

Immunopathologic characterization of the tissue response in endemic pemphigus foliaceus (fogo selvagem)

BACKGROUND: The research on endemic pemphigus foliaceus (fogo selvagem) has mainly focused on the humoral immune response, but little attention has been given to the function of cell-mediated immune response and the nature of the cellular elements of the tissue reaction in the lesions of fogo selvagem. OBJECTIVE: The purpose of this study was the immunophenotype characterization of the inflammatory cells as well as the expression of adhesion molecules and HLA-DR in the perilesional and lesional skin of fogo selvagem. METHODS: Twenty biopsy specimens of lesional and perilesional skin were analyzed by immunohistochemical techniques. The panel of monoclonal antibodies consisted of CD8, CD4, CD1a, HLA-DR, IL-2R, LFA-1, ICAM-1, and PAN-B. RESULTS: The semiquantitative analysis of the cell population revealed a predominance of CD4 T lymphocytes in the tissue response of perilesional and lesional skin. The population of epidermal Langerhans cells was decreased in lesional skin when compared with the perilesional skin, whereas CD1a(+) dermal dendritic cells predominated in lesional skin. Keratinocyte expression of ICAM-1 and HLA-DR was negative in both lesional and perilesional skin. CONCLUSION: The overall results suggest the participation of the cell-mediated immunity in endemic pemphigus foliaceus (fogo selvagem). The lack of keratinocyte ICAM-1 expression may be related to the pattern of cytokines secreted by the CD4(+) T cells of the tissue reaction in fogo selvagem.     

Skin-homing T lymphocytes: detection of cutaneous lymphocyteassociated antigen (CLA) by HECA-452 in normal human skin

The immigration of circulating T cells into specific tissues is directed by the interaction between adhesion molecules on lymphocyte subpopulations and their ligands on vascular endothelium. Of these, endothelial leucocyte adhesion molecule (ELAM-1), weakly expressed in normal human skin (NHS), seems to be the counter-structure for cutaneous lymphocyte-associated antigen (CLA). CLA is a 200 kDa cell-surface glycoprotein of which the sugar moieties sialyl Le(a) and sialyl Le(x) are the possible epitopes recognized by the monoclonal antibody HECA-452. HECA-452 was originally described as a marker for lymphoid organ high endothelial cells, but 16% of peripheral-blood-derived T cells react with this antibody. We studied the expression of CLA on the cellular constituents of the skin immune system (SIS). By applying immunohistochemical double staining, 41% of CD3+ T cells, 44% of CD4+ T cells and 31% of CD8+ T cells were found to express CLA. Keratinocytes, CD1a+ Langerhans cells (LC) and endothelial cells did not express HECA-452 in significant numbers in NHS. Monocytes were found to express HECA-452 in 14% of CD68+ cells. CLA expression was present on a relatively low percentage of T cells and subsets localized distant from NHS vessels, suggesting loss of the molecule during further migration after transendothelial passage. However, intraepidermal T cells expressed CLA in similar percentages to T cells localized directly perivascularly. Our findings support the notion that CLA expression by T cells is associated with their homing into cutaneous structures.     

Epidermal keratinocytes express the adhesion molecule intercellular adhesion molecule-1 in inflammatory dermatoses

Using indirect immunofluorescence assays on frozen tissue sections of skin from healthy subjects and subjects with inflammatory skin diseases, we found that intercellular adhesion molecule-1 (ICAM-1) was expressed in a cell surface pattern on epidermal keratinocytes at the site of lymphoid infiltration in cutaneous dermatoses. ICAM-1 was not expressed on epidermal keratinocytes in noninflamed skin. Its expression was not related solely to epidermal hyperproliferation, as hyperproliferative, tape-stripped epidermis did not express ICAM-1. We have reported previously that ICAM-1 expression on epidermal keratinocytes was upregulated by treatment with interferon gamma and that activated T lymphocytes bound to cultured epidermal keratinocytes in vitro by lymphocyte function associated-1 (LFA-1) molecules on T cells and ICAM-1 on epidermal keratinocytes. Taken together, these data suggest that upregulation of expression of ICAM-1 is an important feature of cutaneous inflammation.     

The effect of in vivo interferon-gamma on the distribution of LFA-1 and ICAM-1 in normal human skin

Lymphocyte function associated antigen 1 (LFA-1) and its ligand intercellular adhesion molecule 1 (ICAM-1) are cell surface adhesion molecules important in many lymphocyte-mediated responses. Recent in vitro studies have demonstrated that the cytokine interferon-gamma (IFN-gamma) can induce ICAM-1 expression by keratinocytes, and that lymphocytes adhere to IFN-gamma treated keratinocytes. In view of the importance of keratinocyte/lymphocyte interactions in the pathogenesis of cutaneous disease, we have examined the effects of in vivo IFN-gamma on cutaneous expression of LFA-1 and ICAM-1. Fourteen volunteers received intradermal IFN-gamma (dose: 1 or 10 micrograms) daily for 3 d. Biopsy was obtained on day 6. Cryostat sections were stained by the peroxidase antiperoxidase technique employing murine monoclonal antibodies to CD11, CD18, and ICAM-1. IFN-gamma intensified ICAM-1 expression by dermal endothelial cells and induced keratinocyte expression of ICAM-1. Furthermore, after administration of 10 micrograms of IFN-gamma LFA-1 positive (LFA + ve) lymphocytes were observed along the basement membrane zone closely related to ICAM-1 + ve basal keratinocytes and also surrounding dermal endothelium. Exposure to IFN-gamma induced expression of both CD11a and CD18 antigens on epidermal Langerhans cells. These studies suggest that the distribution of adherence molecules expression within cutaneous tissue in vivo is modulated by IFN-gamma, and that these alterations may be important in interactions involving cutaneous immunocompetent cells.     

异位性皮炎的记忆性T细胞浸润及ICAM－1表达

为了解粘连分子在异位性皮炎（ＡＤ）炎症及免疫反应过程中的作用，对ＡＤ皮损部位细胞间粘连分子－１（ＩＣＡＭ－１）的表达作了研究。结果虽然正常皮肤表皮不表达ＩＣＡＭ－１，但ＡＤ皮损处角朊细胞则局灶性表达ＩＣＡＭ－１，尤其在有严重单个核细胞浸润及表皮内淋巴细胞移入的部位。免疫表型研究表明，ＡＤ真皮浸润中ＣＤ４＋／ＣＤｗ２９＋／ＣＤ４５ＲＡ－记忆性Ｔ细胞占主导，推测它们可能通过分泌某些细胞因子而诱导角朊细胞表达ＩＣＡＭ－１。ＩＣＡＭ－１与淋巴细胞表面的淋巴细胞功能相关抗原－１（ＬＦＡ－１）之间相互作用可能对淋巴细胞在皮肤内的运行起调控作用。     

The skin immune system (SIS): distribution and immunophenotype of lymphocyte subpopulations in normal human skin

The complexity of immune response-associated cells present in normal human skin was recently redefined as the skin immune system (SIS). In the present study, the exact immunophenotypes of lymphocyte subpopulations with their localizations in normal human skin were determined quantitatively. B cells were not found to be present in normal human skin. Lymphocytes were always of T-cell type, and 90% of these T cells were clustered in 1-3 rows around postcapillary venules of the papillary vascular plexus or adjacent to cutaneous appendages. In such perivascular localizations, they were found to differ from their circulating counterparts in three ways. First, skin perivascular cells were found to be approximately evenly distributed over CD4+ inducer and CD8+ suppressor-cytotoxic T-cell subsets (mean CD4/CD8 ratio: papillary layer 0.96, reticular layer 0.99). Second, within the category of CD4+ inducer T cells, most were phenotyped as CD4+, 4B4+ helper inducer T lymphocytes, whereas CD4+, 2H4+ suppressor inducer T lymphocytes were found to be relatively rare (less than 5%). Third, the majority of skin perivascular T cells were activated as they expressed HLA-DR and interleukin 2 receptors. Intraepidermal, directly subepidermal, and other ("free") lymphocytes were mostly of the CD8+ suppressor-cytotoxic T-cell subset but accounted for less than 10% of the total number of lymphocytes. Intraepidermally localized T cells accounted for less than 2% of the total number of lymphocytes present in normal skin. Our results indicate that preferential perivascular localization of activated T lymphocytes is the characteristic of normal human skin. This might be a reflection of continuous antigen recognition upon endothelial cell presentation and/or continuous T cell-mediated endothelial cell activation thereby inducing enhanced antigen clearing by the skin's endothelium.     

Adhesion molecule expression by epidermal Langerhans cells and lymph node dendritic cells: a comparison

The migration of epidermal Langerhans cells (LC) and their transport of antigen from the skin to draining lymph nodes are of considerable importance in the induction of cutaneous immune responses, including contact sensitization. While in transit to the lymph nodes, LC are subject to a number of phenotypic changes required for their movement from the skin and acquisition of the capacity for antigen presentation. Among these are alterations in the expression of adhesion molecules that regulate interactions with the surrounding tissue matrix and with T lymphocytes. In the study described here, we investigated, using a combination of immunocytochemistry and flow cytometry, the expression by LC, and the lymph node dendritic cells into which they mature, of the three adhesion molecules, E-cadherin, intercellular adhesion molecule-1 (ICAM-1) and the membrane glycoprotein CD44. The migration of LC was associated with a marked reduction in the expression of E-cadherin, but a parallel upregulation of ICAM-1. No change in the expression of CD44 was detectable. The significance of these changes and their relevance for the functional maturation of LC are discussed.     

Absent or low expression of T-cell receptor zeta-chain in T cells infiltrating human pathological skin conditions

The T-cell receptor (TCR) zeta-chain is involved in signal transduction necessary for T-cell activation and subsequent proliferation. Expression of the TCR zeta-chain in vivo has been studied by a variety of technical approaches on different cell and tissue specimen. However, the in situ situation concerning the expression of the TCR zeta-chain has not yet been investigated on infiltrating T lymphocytes in neoplastic and inflammatory cutaneous diseases. In this study, we analysed the expression of the TCR zeta-chain in a number of skin tissues affected by established inflammatory and neoplastic conditions. Serial sections of different tissue specimens were stained immunoenzymatically for CD3 and TCR zeta-chain expression. No or at most scarce expression of TCR zeta-chain was detectable in the inflammatory and neoplastic skin conditions investigated as compared to CD3-positive cells. It is possible that this TCR zeta-chain deletion is induced by the skin microenvironment as an effect of local immunoregulatory influences. Alternatively, lymphocytes located in the skin may generally not express this molecule. In our study, tumour-infiltrating T lymphocytes of CTCL were negative for TCR zeta-chain expression. It has been hypothesized that downregulation of the TCR zeta-chain on tumour-infiltrating T lymphocytes is a mechanism by which neoplastic cells escape the cellular immune response. Our findings showing the absence or reduction of TCR zeta-chain expression also in inflammatory skin lymphocytic infiltrates is not consistent with a pivotal role of the TCR zeta-chain in the process of immune escape of tumour cells.     

Fc epsilon R11/CD23 receptor distribution in patch test reactions to aeroallergens in atopic dermatitis.

There is increasing evidence that exposure to organic allergens may induce or exacerbate lesional skin in patients with atopic dermatitis. In this study, patients with atopic dermatitis were patch tested to 11 common organic allergens and to control chambers containing 0.4% phenol and 50% glycerin in 0.9% saline. In biopsies from positive patch test reactions, patch test control skin, lesional eczematous and non-lesional skin from atopic individuals, and normal skin from non-atopic volunteers, the presence and distribution of macrophages (RFD7+), dendritic cells (RFD1+), and Langerhans cells, and the expression of the low-affinity receptor for IgE (CD23) were investigated. In patch test reactions and lesional skin samples, inflammatory infiltrates of diffusely distributed macrophages (RFD7+), dendritic cells (RFD1+), T lymphocytes (RFTmix+), and Langerhans cells (CD1+) were seen, the latter being present in both the epidermis and the dermis. The numbers of Langerhans cells were reduced in the epidermis and increased in the dermis in patch test reactions and lesional skin compared to their controls. Double staining revealed a change in the distribution of CD23 antigen. In patch test control and non-lesional biopsies many macrophages and only a few Langerhans cells within the dermal infiltrates expressed this antigen. In patch test reaction and lesional skin samples, however, the proportion of CD23+ dermal Langerhans cells had increased compared to macrophages. Furthermore, in these latter samples an increased proportion of dermal CD1+ cells expressed the dendritic cell (RFD1+) marker. These results show that following antigen challenge there are marked similarities between the phenotype of the cellular infiltrate in patch test reaction and lesional skin biopsies, and also demonstrate a changing distribution of CD23 on antigen-presenting cells.     

Adhesion molecules in atopic dermatitis: patch tests elicited by house dust mite

Different T-helper subsets, which are characterized by the secretion of distinct cytokines (Th1, Th2), have been found in house dust mite-exposed skin of sensitized individuals and in nickel-specific T lymphocytes from nickel contact allergic and non-allergic individuals. In order to evaluate the role which adhesion molecules may play in the homing of different T-cell subsets into allergen-exposed skin of atopic and normal individuals, we compared the expression pattern of adhesion molecules in patch test reactions to house dust mite antigen (D.pt.), nickel sulfate (Ni) and the irritant anthralin. Biopsies were taken al various time points after application of these agents and studied by immuncytochemistry. To exclude an endogenous difference in adhesion molecule expression in atopic and non-atopic skin, sequential biopsies from Ni patch tests of 2 normal individuals were also included in this study. The expression of E-selection. P-selection. CD31, VCAM-1 and ICAM-1 on endothelial cells and other cells in the skin was quantified by microscopic evaluation. Skin homing T cells were also quantified using antibodies toCD3, CD4, CDS, UCHL-I, L-selection and the cutaneous lymphocyte antigen (CLA). Independent of the eliciting substance, all lesions showed an up regulation of all adhesion molecules tested, with the exception of CD62. The appearance of E-selection and an increase in ICAM-1 and VCA M-1 expression were first observed at 12 h after application of the various agents. In parallel, the number of CLA+ and L-selection+ lymphocytes increased steadily. No principle differences could be established between the various types of skin reactions in atopic individuals, nor did the skin of patients with AD differ from normal controls. Our results provide evidence that differential expression of adhesion molecules does not play a major part in observed differential homing of Th1 and Th2-cell subsets into patch test sites provoked by house dust mite and nickel sulfate in atopic and non-atopic individuals.     

Imiquimod, a topical immune response modifier, induces migration of Langerhans cells

Langerhans cells are bone marrow derived dendritic cells that represent the major antigen-presenting cells in the skin. Langerhans cells take up and process antigen within the epidermis and present processed antigen to T lymphocyte in the regional lymph nodes and thus form an integral part of the cutaneous immune response. The cutaneous immune response can be modified by a number of pharmacologic agents, including corticosteroids, cyclosporine, and retinoids as well as physical agents, such as ultraviolet light. For the most part these agents act by suppressing immune function. A topical immune response modifier, imiquimod has been shown to enhance the cutaneous immune response. Imiquimod has anti-viral and anti-tumor effects in animal models and has been approved for the topical treatment of external genital and perianal warts in humans. The biologic activity of imiquimod in part is due to its effect as a cytokine inducer. Preliminary data suggested that imiquimod could have an effect on Langerhans cells. In order to clarify this effect on Langerhans cells, we examined Langerhans cell morphology and migration in imiquimod-treated skin. The density of Ia + cells decreased 2 d after treatment, falling to approximately 43% by day 10. The Ia positive in cells remaining in the skin appeared larger and more dendritic suggesting an activated state. ATPase staining of epidermal sheet confirmed the decreased number of Langerhans cells. To clarify status of Langerhans cells, the activation of B7 was examined. Activation of B7-1 or B7-2 was not detected. Imiquimod, however, did enhance Langerhans cell migration from skin to draining lymph nodes. This enhanced Langerhans cell migration was also associated with an enhanced allergic contact hypersensitivity. These results suggest that the mechanism of modulation of immune response by imiquimod is in part due to effects on Langerhans cells.     

Cutaneous T-cell lymphoma lesional epidermal cells activate autologous CD4+ T lymphocytes: involvement of both CD1+OKM5+ and CD1+OKM5- antigen-presenting cells

Cutaneous T-cell lymphoma is characterized by infiltration of the skin by activated CD4+ T lymphocytes. The mechanism by which these T lymphocytes achieve and maintain their activated state is unknown. Antigen-specific activation of T lymphocytes is dependent upon antigen-presenting cells which express HLA-DR class II major histocompatibility complex molecules, such as epidermal Langerhans cells. In addition to CD1+DR+ Langerhans cells, cutaneous T-cell lymphoma lesional epidermis contains major histocompatibility complex class II positive non-Langerhans cell populations, including CD1+OKM5+ bone-marrow-derived cells and DR+ keratinocytes. We asked whether any of these epidermal cell populations demonstrate capacity to activate T lymphocytes. Various numbers of epidermal cells from uninvolved and involved cutaneous T-cell lymphoma plaques were therefore used to stimulate autologous CD4+ and CD8+ T lymphocytes in the absence of exogenous antigen. Involved epidermal cells potently induced proliferation of CD4+ T lymphocytes (S.I. +/- SEM = 466 +/- 45). In contrast, uninvolved epidermal cells only induced background levels of proliferation (S.I. +/- SEM = 2 +/- 0.5, N = 8, p less than 0.01). Neither involved nor uninvolved epidermal cells were able directly to activate CD8+ lymphocytes. The capability of involved epidermal cells to activate CD4+ T lymphocytes was dependent upon CD1+DR+ leukocytes and not DR+ keratinocytes, because depletion of either HLA-DR+, CD1+ or HLe1+ epidermal cells totally abrogated the T-lymphocyte proliferation. Interestingly, on a cell per cell basis CD1+DR+ cells obtained from involved skin, demonstrated relative to CD1+DR+ cells from uninvolved skin, enhanced capacity to activate CD4+ T lymphocytes. Furthermore, CD1+OKM5+ cells from involved epidermis stimulated autologous CD4+ T lymphocytes. This indicates that a unique hitherto undescribed CD1+OKM5+ epidermal antigen-presenting cell population may participate in T-lymphocyte activation. These findings provide support for the concept that the epidermal cells in cutaneous T-cell lymphoma patients, particularly the antigen-presenting cells, may contribute significantly to the activation of CD4+ malignant and/or non-malignant inflammatory T lymphocytes within the skin.     

The interaction between Langerhans cells and CD4+ T cells.

The human skin is increasingly exposed to haptens and environmental protein antigens. Because Langerhans cells represent the outermost network of MHC class II+ antigen presenting cells in mammalians, we investigated their interaction with CD4+ T cells. Hapten-modified Langerhans cells induced proliferation and IL-2 production in naive resting CD4+ T cells. T cells activated in this manner and subsequently cultured with IL-2 mediated contact sensitivity in vivo and produced IL-2 but no IL-4 upon restimulation in vitro. Thus they corresponded to Th1 cells. Repeated stimulation with Langerhans cells induced a modulation of the lymphokine pattern: IL-2- and IL-4-producing Th0-like cells were identified after 3 to 4 rounds of restimulation; after > 5 rounds, Th2-like cells with an IL-4+IL-2- pattern and the capacity for inducing IgE synthesis in B cells was identified. Th2 cells were also recently found to mediate inflammatory tissue lesions containing a cellular infiltrate. This demonstrates that Langerhans cells may activate resting CD4+ T cells, Th1-, Th0- and Th2-like cells. It further shows that Langerhans cells may promote the differentiation of postthymic CD4+ T cells into subsets with distinct immune functions: Th1 cells which have the potential to mediate inflammatory reactions such as allergic contact sensitivity and Th2 cells which may be responsible for abnormalities associated with atopic dermatitis, such as elevated IgE and inflammatory skin lesions containing a cellular infiltrate.